Lot of blunders
Everyone has ups and downs in their rating.
If it troubles you, then you can do some unrated warm up games (for example against a computer https://www.chess.com/play/computer) or puzzles, and if you feel like you're not seeing things well that day, then don't play any rated games.
And if you're an "oldie" then maybe you have more bad days than me, but we all have days where it seems like we can't calculate well or concentrate. In the last 90 days you've been over 1000 multiple times, so I have to think if you keep playing it's only a matter of time until you get there again.